mars’ orbit - nasa · to surface habitat. memusleft on surface to minimize dust contamination of...

Mars’ Orbit

Opportunity Sun Images

HLS2 Hangouts - Environmental Considerations for a Human Base on Mars P. 1

Daytime Surface Temperature

Approximate Northern Summer Solstice Approximate Northern Winter Solstice


Night Surface Temperature

Approximate Northern Summer Solstice Approximate Northern Winter Solstice


Near Surface Temperature

Surface Thermal Gradient

• Recent data from Opportunity– At sunset 5°C temperature drop over

1.3m height difference

– 2 hours after sunset 10°C drop over 1.3m height different

• Several Mars years of data available from temperature sensors on Spirit, Opportunity, and Curiosity

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Dust Thermal Effects

Diurnal Temperature

• Large amounts of dust in the atmosphere attenuates diurnal temperature changes

• Major storms can decrease average temperatures to levels that require maintenance/survival heating even in summer

Southern Winter Solstice Southern Summer Solstice

2007 Global Dust Storm

Tau data courtesy of Dr. Mark Lemmon, Texas A&M


Dust Thermal Effects

Global Dust Storms

• Occur approximately every 3 Mars years

• Storm intensity varies across Martian surface– Spirit & Opportunity affected

differently

• New models may help predict storm years

Tau data courtesy of Dr. Mark Lemmon, Texas A&M

39%

Direct Light Transmission

5.5%


1.6%


2.2%


0.9%



Dust Effects

Dust Loading

• Dust settles on surfaces– Can be removed by wind

or active systems

• Texture, material, and geometry, and vehicle location affect how much dust can be removed

Sol 332 (12/30/04) Sol 2814 (12/24/11)

Images credit: NASA/JPL/Cornell/ASU


Dust Effects

Dust Loading

• Dust can be transported across vehicle surfaces by wind or vibration– Magnitude of movement affected by tilt of

dust covered surface

Sol 4315 (3/14/16)HLS2 Hangouts - Environmental Considerations for a Human Base on Mars P. 8

Dust Effects

Contamination

• Dust sticking to lenses reduces effective resolution which can limit operations– Can correct for some

contamination

• Static binding to surfaces can render instruments unusable

Sol 16 (2/2/04) Sol 4408 (6/17/16)


Thermal Effects

Battery Capacity

• Battery capacity is a function of battery temperature– Colder batteries hold less charge

– Up to a 20% change difference between winter and summer

Component Heating Requirements• Seasonal variation

• Affected by:– Surface thermal inertia

– Height above surface

– Shadowing

– Component thermal inertia


Thermal Effects

Mars Arrival SeasonYear Ls Northern Season Southern Season Reference

2001 259 Late Fall Late Spring (ODY arrival)*

2004 339 Late Winter Late Summer (MERB Landing)

2006 22 Early Spring Early Fall (MRO arrival)

2008 76 Late Spring Late Fall (PHX landing)

2012 150 Late Summer Late Winter (MSL landing)

2014 201 Early Fall Early Spring (MAVEN arrival)

2016 245 Late Fall Late Spring (ESA EDM landing)

2018 295 Early Winter Early Summer (InSIGHT landing)**

*Global Dust Storm Year

**Global Dust Storm Season (prediction)


The Mars Environment and Its Effects on Human Exploration

Larry Toups, NASA/Johnson Space Center


Example Mars Surface Field Station and Surrounding Regions of Interest

(ROIs) – Jezero Crater

Exploration Zone

Science ROIs

ISRU ROIs

Science ROIs

ISRU ROIs

Science ROIs

Engineering ConsiderationsSite Buildup Considerations and

Constraints


Surface System Elements Needed for the Surface Field Station Emplacement Phase

• Mars Ascent Vehicle (MAV)

• Crew Descent Module

• Atmospheric ISRU

• Power (4 x 10 kW units)

• Robotic Rovers

– Special regions– Crew support

• Cargo Off-loading

• Habitation

• Tunnel

• Science payloads

• Mobility platform to reposition

payloads

• Small unpressurized rover (crew)

• Small pressurized rover (crew)

• Logistics modules

• Logistics

– Crew consumables– Fixed system spares– Mobile system spares– EVA spares

1 km

Lander-1Power

Lander-2Mars Ascent Vehicle

MAV

Lander-3Logistics

Lander-4Habitation Crew Arrival

100 m dia designated landing site1 km radius plume ejecta hazard zone (typ) HLS2 Hangouts - Environmental Considerations for a Human Base on Mars P. 14

Potential Mars Environment Element Design Drivers

Seasonal changes

• Daylight (at 50 deg N latitude):– ~15 hrs (summer solstice)

– ~9 hrs (winter solstice)

Temperature range (extremes)

• Highs > ~20°C• Lows < ~ -110°C

– < −153°C (120 K; −243°F) during the polar night

Winds

• Winds: typically < 20 m/s with low dynamic pressure• Wind speeds measured by Viking landers

– Maximum: 30 m/s (60 mph)

– Average: 10 m/s (20 mph)

• Low atmospheric density (<1% of Earth’s) means the wind is not strong as compared to Earth (hurricane-force winds would “feel like” a slight breeze)

– Periodic Dust Storms HLS2 Hangouts - Environmental Considerations for a Human Base on Mars P. 15

Summer Solstice (Ls=90)

Temperature and Winds : Jezero Crater

Temperature

Wind Speed on MarsDynamic Pressure

(MB)

"Feels like" wind speed on Earth (at

STP)

mph m/s m/s mph

10 4.5 0.2367 0.6 1.4

50 22.4 5.9169 3.0 6.8

67 30.0* 10.6587 4.1 9.1

100 44.7 23.6677 6.1 13.5

150 67.1 53.2523 9.1 20.3

200 89.4 94.6708 12.1 27.1

224 100.0 118.4304 13.5 30.3

447 200.0 473.7216 27.1 60.6

500 223.5 591.6924 30.3 67.7

Wind Velocity, Direction @ 1.6 m, 3 m, and 10 m Altitude

• Several Mars environmental models have been built using remote sensing data gathered from a variety of orbiting spacecraft

• These models are being used to develop site-specific environmental data for use in surface system preliminary concept design

• This slide shows examples of temperature and wind results at Jezero Crater

5.2 m/sWinter Solstice (Ls=270)

7.8 m/s


Environmental Influences on Mars Surface Operations

As seen from the surface:

Global Dust Storm


Some Questions to Consider on Element Designs

• Habitats - How do you build a hab where crew is ingressing potentially multiple times a day,

with potentially toxic perchlorates on the suits?

– Accumulated dust: Exterior Windows, radiators– Abrasion damage: Hatch seals & locking mechanisms– Chemical interactions: water processing, food safety

• Rovers - How are (Pressurized and Unpressurized) Rovers affected by the surface

environment?

– Accumulated dust: windows, radiators, external batteries (possible overheating)– Abrasion damage: moving parts, hatch seals & locking mechanisms

• Power Systems – Are power systems affected?

– Accumulated dust: solar arrays, nuclear power radiators

• EVA Systems

– Abrasion damage: suit fabrics, helmet face shields, EVA tool moving parts– Accumulated dust: helmet face shields, boots (tracking into habitat)


• If we pursue a site that is further north, potentially for sub-surface ice

– Does that affect the efficiencies of solar arrays?– Does the thermal environment influence the overall design of the equipment?

• How do seasonal temperatures and albedo (dust) variations play in?

• How do Planetary Protection protocols affect surface systems designs and operations?

– Since there could be “critters” that may be part of the natural environment

Some Questions to Consider on Element Designs


Some Questions to Consider on Surface OperationsExample: Dust Storm Operations

Since dust storms are a certainty, we need to define what we would/ wouldn’t do during a storm

• If solar power: what has to be powered down?– What is the abort criteria to abandon the surface and return to orbit?

• What’s the visibility go/no-go criteria for EVA or rover ops?– Are there knowledge gaps that must be filled to answer this question?

– Is there a niche for tele-robotic rover ops during dust storms?

• If rover is TBD km from the Habitat when a dust storm hits, should the rover shelter in place or try to return to the Hab?– How will dust storm considerations or storm contingency operations influence the surface rover

design?

• What are the post-storm procedures?– What needs to be checked/cleared of dust?

• What are the implications for use of optical communications technology?


National Aeronautics and Space Administration

EVA EnvironmentsOverview for Human Landing Site Study

Google Hangout

July 28, 2016J. Buffington/JSC-XXR. Blanco/JSC-ECL. Aitchison/JSC-EC


Pre-decisional, For Internal Use Only

ExtravehicularActivity Management Office

• Extravehicular Activity (EVA) or “spacewalks” brings humans as close to the environment outside a spacecraft as humanly possible

• Two basic questions in EVA System Design: • Where are you going?

– Defines environmental factors affecting design• What are you doing?

– Identifies system mobility and vehicle/tool interfaces• Unfortunately we have gaps in our understanding, and even with what we do know we see gaps

in our technological solutions – no one single EVA Suit design (today) is able to operate in all environments humans might conduct a spacewalk in

• As Human Spaceflight matures towards a Mars Surface Mission, EVA is working to close gaps in knowledge and technology necessary to address significant challenges including the Environment

Planning for EVA




Notional Mars Mission EVA Concept

Four mEMUs are launched on separate logistics flight and rendezvous with stack in Mars orbit for check-out.

Transit stack with xPLSSstays in orbit until crew returns in OCSS for Earth transit.

Wearing mEMUeliminates need for additional EVA prep prior to transit to surface habitat.

mEMUs left on surface to minimize dust contamination of in orbit vehicle an increase surface logistics/spares.

OCSS EVA with umbilical used for contingency EVA transfer to cis-lunar stack.

Will use in-orbit xPLSS and EVA kits from previous missions for Mars transit.




EVA System Drivers

ISS Cis-Lunar Space Mars Surface

EVA Tasks • Vehicle assembly and maintenance

• Science• Vehicle maintenance

• Science• Vehicle maintenance

Environment • Microgravity• Vacuum• Sharp edges from

micrometeorite strikes• Relatively constant

temperature zones

• Microgravity and 1/6th-g• Vacuum• Sharp edges from

micrometeorite strikes• Loose dust/dirt• Increased radiation exposure

• 3/8th-g• Non-vacuum• Chemically reactive soil• Loose dirt/dust• Seasonally variable

temperatures

EVA Duration Plan 5 -7h + 30min Plan 4 - 8h + 1h Plan 2 – 8h + 1h

EVA Frequency • Up to 8 per year • In orbit, 10 per year• Surface, up to 24h per week

for <1 yr

• Up to 24h per week for > 1 yr

Maintenance Cycle • Standard 90/180/360d processing

• Focused hardware checks for 2 weeks prior to EVA

• Automated operations for standard processing

• In orbit, Focused hardware checks for 1 week prior to EVA

• Surface 1h pre/post EVA

• Automated operations for standard processing

• Surface 1h pre/post EVA

Re-supply Frequency 10+ cargo flights per year Up to 2 cargo flights per year Pre-positioned supplies

Communication Delay <1 sec 1 -3 sec 3 – 21 min




EVA Technology Gaps

• Dust Tolerant Mechanisms

• Textiles for High Abrasion

Environments

• Thermal Insulation for Non-vacuum

Environments

• Dust Mitigation Strategy for

Remote Habitats

• Mass Reduction Strategies

• Closed Loop Life Support Systems




EVA Technology Gaps

Dust Tolerant Mechanisms• Space suits for planetary exploration will be

required to operate nominally in a coarse dirt and fine dust environment for up to 600 hrs with minimal maintenance required.

• Nominal operation is considered less than 10% increase in running torque for bearings, less than 10% increase in actuation torque for disconnects, and less than 2 sccm increase in leakage.

• Key mechanisms in space suits include – Quick disconnects for oxygen, water, and

power/data lines; gas exhaust ports, relief and purge valves

– Bearings in the pressure garment arms, legs, and waist

– Component hard disconnects at the pressure garment wrist, arm, waist thigh, and ankle; and hinges at the pressure garment rear hatch.

Desired Technology Capabilities:• Mechanisms with quick change-out dust seals• Mechanisms with active dust repellant properties




EVA Technology Gaps

Textiles for High Abrasion Environments• NASA needs suit material(s) and systems of layers of

materials that are capable of long duration exposure to dust, and abrasive activities that are also flexible so as not to compromise mobility (walking, kneeling, etc. ).

Desired Technology Capabilities:• Self-healing textiles• Damage sensing textiles• Manufacturing techniques to minimize dust migration

between textile layers• Textiles or coatings with active dust repellant features• Textiles or coatings with passive dust repellant

features




EVA Technology Gaps

Thermal Insulation for Non-Vacuum

Environments• Current space suit insulation technologies rely heavily

on the vacuum of the low-earth orbit environment to minimize heat transfer by separation of layers in the space suit material lay-up so that conduction, as well as convection

• However, various exploration destinations, and specifically Mars, exhibit low pressure atmosphere which allows convection to occur

Desired Technology Capabilities:• Lightweight, flexible, durable, and thin to minimize

interference with mobility features of suits (Note: If one or more of the above characteristics is an issue, but could be resolved for space suit application through development, the technology is of interest)

• Adaptable for seasonal variations in temperature




EVA Technology Gaps

Dust Mitigation Strategy for Remote

Habitats• Exclusion of dust from habitable environments is a

system level challenge. • Space suited crewmembers will bring some amount

of dust into the habitat following each EVA. In reduced gravity environments fine dust does not quickly settle out of the habitat atmosphere.

Desired Technology Capabilities:• System to remove/repel dust from space suits• System to remove and collect dust from the habitat

atmosphere• System to remove and collect dust from habitat

surfaces• System of locks that employ the above to mitigate

dust in the habitable volumes




EVA Technology Gaps

Mass Reduction Strategies• Launch mass from Earth’s surface has always been a

challenge but introduction of gravity environment for EVA will create greater need for reduced on-back mass.

• Gravity environments will increase the need for finer alignment of EVA suit system CG to optimize mobility and efficiency.

Desired Technology Capabilities:• Composite lay-ups that meet load requirements

(pressure and impact) with minimal mass• High reliability (low scap rate) methods for fabricating

complex composite geometries• In-situ printing of replacement suit components• Lightweight bearings




EVA Technology Gaps

Closed Loop Life Support Systems• NASA needs EVA CO2 and H2O removal system

that is low mass, low power, low consumable at the mission architecture level, minimizes exhaust pollutions (for planetary protection considerations), and functions within the Mars CO2 atmosphere and convective thermal environment.

Desired Technology Capabilities:• Small package that enables the overall Portable

Life Support System (PLSS) volume to be minimized. Current technologies have dimensions 10.5 in x 8in x 6in.

• Remove CO2 at rates up to 190 g/hr with concentrations <2mmHg

• Accommodate these removal rates for up to 12hrs with 8hrs of autonomous EVA time and potentially 4hrs of prebreathe time.

• Remove H2O vapor at rates up to 150 g/hr with <75% RH in oxygen carrier gas with trace CO2




• The EVA Community is actively working to collaborate with scientists and engineers across spaceflight • Participate in intra-agency technical interchange meetings

– Human Research Program Annual Workshop– EVA Collaboration Workshop

• Maintain high-level list of technology and knowledge gaps with associated closure plans

– EVA System Maturation Team – NASA Technology Roadmap

• Partner across Government, Industry, and Academia to strategically target gap areas by priority with emphasis on cross-cutting areas

– Small Business Innovative Research Program– Space Act Agreements– Research grants (NSTRF, NAIC, NSBRI, etc.)

• Publish latest technical developments and research results in relevant publicly accessible forums

– Conference papers (AIAA, ICES, SAFE, IFAI, SAMPE, etc.)– Trade publications– NASA Tech Briefs

• Through sharing of knowledge, it is our hope that we are closing the gaps to EVAs on Mars

Closing EVA Gaps


Mike Fincke, Astronaut Office

NASA’s Journey to Mars:

EVAs in gravity

Long Way from Home


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